Over the years when four or more legs or other support members have been used, problems have arisen unless the terminus end of all such members lie in the same plane and the surface on which they rest is flat.
On the other hand, if any one of the support members does not lie in a plane with the remaining support members or, if the terminus ends lie in the same plane but the support surface is uneven, then a rocking motion can occur. The more out of plane or the more uneven the surface, the more exaggerated the rocking motion can become when weight is shifted on the article being supported.
To overcome the above mentioned problems, springs have been used on the terminus portion of the supports as well as pliable rubber and similar resilient means to compensate for unevenness.
The problem with these prior known supports is that the compressed terminus or terminuses have bias pressure to return to their original position when weight is shifted on the article being supported, this can actually amplify the rocking motion rather then preventing it.
Spring dampening means have been tried utilizing viscous material such as bounce putty to dampen spring motion of support terminuses. The hard outer casing, however, would not conform to support surface irregularities and if the casing were soft, the piston therein would not work.
The age old solution to the rocking problem are support feet with threaded shafts that can be longitudinally adjusted up or down to compensate for uneven surfaces. First, this requires the laborious job of getting adjacent to the support surface such as the floor to screw the support feet in or out of the support structure such as chair legs, etc. Also, when the supported structure is moved to a different location or is turned to a different orientation, further adjusting of the support feet may be required to again obtain equal pressure on all legs to prevent rocking.